Water tube boiler



March 17, 1936. J. JOHNSON WATER TUBE BOILER Filed March. 11, 1935 3 Sheets-Sheet l AYLSOTL March 17, 1936. J. JOHNSON 2,034,237

WATER TUBE BOILER .Filed March 11, 1935 3 Sheets-Sheet 2 on c co common cuocooo uOcOOOO oocoooo oooooo 0000000 March 17, 1936.. J, JOHNSON WATER TUBE BOILER Filed March 11, 1935 3 Sheets-$heet 3 Q] j nson/ Patented Mar. 17, 1936 UNITED STATES PATENT OFFICE Application March 11, 1935, Serial No. 10,554 In Great Britain March 29, 1934 3 Claims.

The invention relates to water-tube boilers of the one-drum type having steam-generating U- tubes projecting downwardly from the steam drum on the two sides of the combustion chamber, and its main object is to provide an improved type of such a boiler, which shall be lighter and less bulky than comparable types, and consequently by virtue of the latter characteristics, particularly suitable for naval purposes.

With such a main object, the invention consists in improved water-tube boilers comprising the combinations of elements hereinafter set'forth and particularly pointed out in the claims.

Referring to the accompanying drawings, which are of a diagrammatic nature:-

Figure 1 shows an end elevation partly in section of one form of the invention having outwardly-curved U-loo-ps juxtaposed at the lower part of the boiler,

Figure 2 being a corresponding sectional plan;

Figure 3 shows an end elevation partly in section of a form of the invention in which the superheater tubes are secured direct to the drum,

Figure 4 being a corresponding sectional plan, and

Figure 5 a sketch of one form of end wall;

Figure 6 shows a modification of the superheater arrangement of Figure 3, in which the superheater tubes are secured to a drum or header connected to the main steam drum by a pipe; while finally Figure 7 shows a sketch of the steam drum fitted with one form of forced water circulation.

The same reference symbols are used in the different drawings to denote corresponding parts.

In carrying the invention into effect according to one form, (see Figures 1 and 2) a steam drum, A, is provided at the top of the boiler and to this drum are secured banks of tubes, 2, 2, in the form of outwardly-curved Us nested one within the other, and symmetrically arranged on the two sides of the boiler so as to surround the combustion chamber, B, the legs of any individual loop being disposed on the same side of the centre plane as shown.

Each U consists of a simple looped tube, i, e., a tube without internal tubes such as are pro-. vided in Field tubes, so that by virtue merely of their configuration and disposition, a definite circulation as hereinafter described is automatically established with a structure of maximum simplicity.

The Us preferably lie in planes substantially at right angles to the axis of the drum, A, so that each U has one leg, 2a, nearer the source of heat and the other leg, 2b, more remote therefrom, the leg of each U, such as 2b, more remote from the source of heat thus serving as a downcomer to the riser leg of the same U, 2a, disposed nearer the combustion chamber, B.

Taking, by way, of example, those Us having legs immediately adjacent to the furnace, it will be seen that each consists in a leg, 2a, expanded or otherwise secured at its upper end to the drum, A, and curving outwardly thence to return to a point, C, at the bottom of the combustion chamber as near as may be to the centre plane of the boiler, the tube then making a. return bend in a direction away from the centre plane and passing back to the drum by way of the other leg 2b, of the U which is situated more remote from the combustion chamber.

The return bends may conveniently have a radius sufficient to permit of the introduction of a cleaning tool.

In the more or less crescent-shaped space between the risers and downcomers, a superheater, D, comprising a series of tubes, 5, attached to headers or to a partitioned drum, 5, (see Figure 2) which may be straight or curved to follow the shape of the Us, is arranged so that its tubes run horizontally, or alternatively, a superheater, D, may be provided on one side of the boiler and a feed-water heater or reheater, E, on the other.

One form of water-tube back wall is indicated at l, in Figure 2, and another example will be described in detail below; any known form of water wall with headers or drums may, however, be substituted.

For high duties, the front end of the boiler in the case .of liquid fuel isalmost wholly occupied by burners but when only a comparatively few burners are required, the space not so occupied may be similarly provided with a water-tube wall.

Oil burners in the different figures are denoted by the letter F.

According to another form of the invention, the superheater drums or headers, 6, are dispensed with (see Figure 3) and the superheater tubes, 8, 8, are secured direct to the steam drum, A, a suitable pocket or trough, 9, with outlet (not shown) provided therein being provided for the reception of the superheated steam.

According to this form of the invention, the water-tubes may be formed in grids comprising a number of Us, 2, 2, nested one within the other in a plane at right angles to the axis of the steam drum, A, these units being held in place by clips or the like, such as H], so that they can be secured to the or withdrawn as a whole.

The superheater tubes, 8, 8, are conveniently formed in the same manner, in grids with clips, I I, the arrangement being such that grid units of superheater tubes and grid units of watertubes alternate along the length of the boiler (see Figure 4) or a part thereof, the clips serving the purpose of regulating the position of these tubes in relation to one another both in a transverse and longitudinal direction.

Any other suitable means may, however, be provided for supporting and/or preventing oscillatory movement of the tube system.

In Figures 4 and 5, one suitable form of rear wall is shown by way of example, this form comprising on each side of the centre line of the boiler, two groups of nested U-loops, l2 and I3,

'each group consisting of six loops in a plane at right angles to the axis of the steam drum. The outer legs, l2a and [3a, of the U-loops, on a given side of the boiler coincide as seen in end View but the corresponding inner legs, l2b and 132), are spaced apart transversely (see Figure 5) so that a substantial area of the rear wall is covered.

The ends of all the loops are expanded or otherwise secured to the steam drum, A.

A modification of the superheater arrangement of Figure 3 is shown in Figure 6, from which it will be seen that while retaining the alternate disposition of the units of water-tubes, 2, and superheater tubes, 8, the ends of the latter are not connected direct to the steam drum, A, but to a header, l4, having a partition or wall, I5, to provide a saturated-steam chamber, Ma, and a superheated-steam chamber, Mb, the chamber, Ma, being connected to the steam space of the drum, A, by the pipe, l6.

At low ratings, boilers in accordance with the present invention work satisfactorily owing to the natural circulation set up, but at higher ratings, it is desirable to provide some suitable form of augmented circulation, and this may be applied to all the water-tubes or to only those whose legs are nearer the source of heat with their corresponding downcomers.

To secure these results according to one form, pockets, lBa, l6a, are provided within the drum, A, corresponding to the tubes through which the circulation is to be forced, (see Figures 3 and 7) these pockets being connected by suitable connections, ll, outside the steam drum, A, to a pipe, l8, in which works a propeller, I9, driven by any suitable source of power. With such an arrangement, the propeller draws water from the lower part of the drum and by way of the connections, l1, and pockets, l6, forces it down the downcomer legs of the U-loops.

Any other suitable water-circulating agent,

. such as a pump, may, however, be used a duct, '28, on each side leading to the funnel or elsewhere.

This duct may be divided by a partition, 21', (see Figure 3) into two, controlled by dampers, 22, or otherwise, so that the degree of superheating and feed-water heating or reheating may 7 a very large heating surface in relation to its volume, so that the resulting boiler has the qualities of light weight and fast steaming which render it suitable in particular for comparatively small high-speed vessels.

Boilers according to the present invention are particularly suitable for burning pulverized coal, oil or colloidal fuel.

It will be understood that variations may be made in the particular structural features described above without exceeding the scope of the invention.

Having now described my invention, what I claim as new and desire to secure by Letters Patent 1. A water-tube boiler comprising, in combination, a single horizontal drum and connected thereto to form a structure symmetrical about the vertical centre plane passing through the axis o said drum, two series of single U-tubes, with their planes disposed transversely to the axis of said drum, one series on each side of said centre plane, the U-tubes of each of said series being convexed outwardly and'having their return bends closely approximated to said centre plane to en close between them a combustion chamber of approximately cylindrical shape with its axis parallel to the axis of said drum. 7

2. A water tube boiler as claimed in claim 1, in which the planes of said U-tubes are disposed transversely to the axis of said drum, and a pocket is disposed in said drum into which the legs of said U -tubes more remote from said combustion chamber open, together with means for establishing an augmented circulation through said U -tubes by way of said pocket and said U-tube legs opening thereinto.

3. A water-tube boiler comprising, in combination, a substantially horizontal drum and connected thereto two longitudinal banks of simple U-looped water tubes with the planes of the Us disposed at right angles to the axis of said drum, one bank on each side of said drum, the U-loops of each of said banks being convexed in their respective planes away from the vertical centre plane through the axis of said drum and having their return bends juxtaposed to said centre plane to enclose between them a combustion chamber, so that by virtue of the configuration of said -U-loops and their disposition in relation to said combustion chamber, an automatic circulation is established within each U-loop in a direction down the'legof said U-loop remote from said combustion chamber and up the leg of said same U-loop adjacent said combustion chamber.

JOHN JOHNSON. 

